The portable and modular cardiopulmonary bypass apparatus has met the above mentioned needs. The apparatus consists of (i) a first cannula assembly means for withdrawing blood from a patient, (ii) a pump means connected to the first cannula assembly means for receiving the withdrawn blood and for moving the blood through the apparatus, and (iii) a first tubing means connected to the pump means to transport the patient's blood away from the pump means. The apparatus further comprises (iv) oxygenator means for receiving blood from the first tubing means and for oxygenating the blood and (v) second cannula assembly means connected to the oxygenator means for returning the oxygenated blood to the patient. The apparatus is portable so that it can be used by medical personnel anywhere. In addition, the apparatus is adapted to include one or more modules for conditioning the blood, such as modules that include a heat exchanger, blood purifier, plasma and blood cell apheresis device and others. An aortic balloon catheter is also provided.